Genetics, Conception & BirthChapter 2

2.1

Genetic Foundations • We carry a “genetic code” – Inherited from parents

• Fertilized human egg– Carries human code

• Begin life as a single cell– Contains our entire genetic code

• (Human egg about to pop)

Chromosomes• Nucleus of each human cell contains– Chromosomes• Thread-like structures made up of deoxyribonucleic

acid, or DNA

– DNA• Complex molecule that has a double helix shape &

contains genetic information– Unique to all (except identical twins)

» Same genetic code

Genes

• Genes– Units of hereditary information composed of DNA.

• Short segments of DNA

– Direct cells to reproduce themselves– Manufacture proteins that maintain life• Blueprint for cell reproduction

Human Genome Project 2003

• Genome–Complete genetic information (DNA) of an

organism • Preliminary map of human genome –Complete set of developmental instructions

for creating proteins that initiate making of a human organism

• Humans about 30,000 genes

Genetic Expression

• Genetic expression affected by their environmental conditions– Hormones in blood stream • Turn genes on/off

– Hormones affected by environmental conditions such as• Light• Day length• Nutrition• Behavior

Genetic Expression

• Numerous studies show– External events outside • Original cell• Person

• +– Events inside cell• Can excite or inhibit gene expression

– Stress• Hormone: cortisol

– 5 fold increase in DNA damage» Woman who is pregnant , 4 yr old son missing

Genetic Principles

• Dominant-Recessive Genes Principle– Recessive gene is influential only if both genes

are recessive– 1 gene of a pair always exerts its effects examples: hair color

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Genetic Foundations

Dominant-Recessive Genes Principle

• Dominant– 1 gene of pair always exerts its effects

• Recessive gene– Exerts influence only if 2 genes of a pair are both

recessive • may be overridden by dominant gene• may be carried from generation to generation but not

expressed in phenotype– Red hair

Genotype & Phenotype

• Genotype–All of a person’s genetic material

Genotype & Phenotype• Phenotype –Observable characteristics –Phenotypes include • Physical characteristics–Height–Weight–Hair color

• Psychological characteristics–Personality– Intelligence

Genetic Principles

• What determines how a genotype is expressed to create a particular phenotype?–Ex: Look exactly like sister/brother?• Same genetics–Why not?

–Science not totally sure

Genetic Principles

• Sex-Linked Genes: X-linked inheritance– Mutated gene carried on X chromosome– Males have only 1 X chromosome– More vulnerable to X-linked disorders • Hemophilia• Fragile-X syndrome